1. you smoke in the same room.
2. the room is too hot.
3. your house has air bourne particulates. (dust)
4. you touch the lens when instaling it.
5. you lose power alot and the bulb cannot cool properly
These 5 things are major factors in why your bulbs are burning out. Most bulbs don't die prematurly... they are murdered. keep em cool and clean and they will last 3 to 5 thousand hours.
Shane54
November 2012